The present invention relates to an internal mixer for mixing and/or kneading materials together.
An internal mixer of a type to which the present invention pertains generally comprises, as shown in FIG. 1 of the accompanying drawings, a mixer body or casing 1 having a generally epitrochoidal mixing chamber 5 with a pair of rotors 6 drivingly housed therein, an upright chute or hopper 2 upstanding from top of the mixer body 1 with its interior communicated with the mixing chamber 5 for the supply of a material to be mixed into the mixing chamber 5, and a floating weight 4 supported within the hopper 2 for movement between lifted and lowered positions and operable to urge the material to be mixed, which has been introduced in a predetermined quantity into the hopper 2 through a supply gate 3, towards the mixing chamber 5 as it is driven from the lifted position towards the lowered position and at the same time to close the opening leading from the interior of the hopper 2 to the mixing chamber 5. The material loaded into the mixing chamber 5 in the manner described above is uniformly mixed when the rotors 6 are driven in the opposite directions with respect to each other, and after it has been mixed uniformly, the mixed material is discharged exteriorly of the mixing chamber 5 by opening a drop-out door 7 arranged and supported at a lower region of the mixer body 1. In this prior art internal mixer, the floating weight 4 must be imparted a cushioning effect in its direction of movement in order for a good mixing result to be obtained.
According to the prior art, as an actuator for the floating weight 4, a pneumatic cylinder 8 is utilized as mounted on the top of the hopper 2 in axial alignment therewith while a piston member 9 inside the cylinder 8 is operatively coupled to the floating weight 4 through a piston rod 10, such that when compressed air is introduced into and purged out from the cylinder chamber 11, one at a time, the floating weight 4 can be moved from the lifted position towards the lowered position and from the lowered position towards the lifted position, respectively.
With the above described prior art internal mixer, it has been found that, since a large amount of air is necessarily discharged to the atmosphere when the floating weight 4 is moved to the lifted position in readiness for the supply of the material to be mixed into the hopper 2 through the gate 3, a loss of energy is too great. Because of this, a compressor of relatively large displacement has to be operated for a substantially extended period of time, and this tends to pose another problem in that a high running cost is incurred.
In addition, the cylinder 8 upstanding on the top of the hopper 2, must have a great stroke for the movement of the piston member 9 in order for the floating weight 4 to be moved within the hopper 2 over substantially the entire length thereof, resulting in the increased height of the machine as a whole. This, in turn, requires a high-roofed or high-raise building for the accommodation of the mixing machine, and therefore, the installation of such a prior art mixing machine is accompanied by the increased cost for the construction of the building.